Multiple-cylinder reciprocating air and like pump



Feb. 14, 1928; 1,659,238

R. D. BOYCE MULTIPLE CYLINDER RECIPROCATING AIR AND LIKE PUMP Filed Oct. 26, 1926 3 Sheets-Sheet l I n uenfor,

R. D. BOYCE MULTIPLE CYLINDER RECIPROCATING AIR AND LIKE FUMP Feb. 14, 1928. 1,659,238

Filed 00:. 26. 1926 s sheets-sheet 2 Feb. 14, 1928. 1,659,238

7 R. D. BOYCE MULTIPLE CYLINDER REQIPROCATING AIR AND LIKE PUMP Filed Oct. 26. 1926 3 Sheets-Sheet 3 I Inuenfor,

Patented Feb. 14, 1928.

UNITED STATES REGINALD DONOVAN BOYCE, OF HENDON, LONDON, ENGLAND.

MULTIPLE-CYLINDER RECIPROCATIN G AIR AND LIKE PUMP.

Application filed October 26, 1926. Serial No. 144,210.

This invention relates to improvements in multiple-cylinder reciprocating air and like pumps wherein the cylinders are arranged around and parallel to the axis of a single rotary shaft having fast upon it a flywheel or the like from the face of which project a series of pillars of unequal effective lengths carrying rollers adapted to maintain contact with the face of a swash-plate for imparting reciprocating motion to the pistons.

In a prior construction of such a pump, as described and claimed in the specification of my British Letters Patent N01 170,786, the pistons are connected with the swashplate by ball-and-socket jointed connecting rods, and means have to be provided to restrain any tendency of the swash-plate to rotate. If, in order to eliminate that tendency, the employment of ball-and-socket jointed connecting rods be eliminated and the pistons be forced towards the swash-plate by springs, difliculty is encountered in assembling the parts, especially if the pistons are provided with piston-rings, on account of the springs tending to eject the pistons (with their piston-rings) from the cylinders before the swash-plate is in position.

The primary object of the present invention is to overcome the difliculty just re- 8b ferred to, and for this purpose, according to' the invention, each piston is urged in the rearward direction by a spring coiled in compression between the rear end of the cylinder and a collar on a rearward extenzs sion of the piston, said extension being of reduced diameter so as to present an annular shoulder at its junction with the main or working portion of the piston, .whilst a set screw adjustable through a threaded hole H) in the cylinder wall is adapted to be projected inwardsso asto engage said shoulder in order to obstruct the rearward movement of the piston under the action of its. spring.

Each spring may be ofsnbstantially coni- 15 cal form when extended, so as to be adapted to occupy the shortest practicable axial length when compressed. The rearward extension of each piston may likewise be substantially conical so as to conform to the 0 shape of the spring when occupying its most rearward position. Preferably, also, the extremity of the rearward extension of each piston is domed to contact directly with the front face of the swash-plate. 5 It will be perceived that the arrangement described renders possible and easy the gradual forcing of each piston rearward as each of its several piston-rings is sprung into the corresponding cylinder, and the retention of the several pistons until after the swash-plate and other parts have been assembled. Conversely the pistons may be forced back successively by the swash-plate of an assembled pump and each retained in such position in turn, thus permitting the demounting of the swash-plate, if necessary, without the inconvenience due to the action of the springs upon the pistons.

In order, as far as possible, to reduce grinding friction between the swash-plate and the rollers, the periphery of each roller may be formed as the frustum of a sphere,

the radius of the sphere being the same for all the rollers, and the rear face of the swash-plate presenting an annular track havinga concave cross-section curved to the same radius; the arrangement beingsuch that, during working, line-contact is maintained between said track and each roller in all positions relatively to one another of the swash-plate and the flywheel or the like which carries the rollers.

The front ends of all the cylinders may be closed by a single hollow plate whereof the interior is divided by a partition into a central inlet chamber and an annular delivery chamber surrounding said inlet chamber; spring-closed inlet and outlet valves affording connnunication between each cylinder and the respective chambers.

One form of the invention, as applied to an air-compressor, is illustrated in the acron'ipanying drawings, wherein Figure l is a sectional side elevation of the pump, the section being taken on line 11 of Figure 2. Figure 2 is an internal'face view of the left-hand portion of the casing seen in F igure 1, the right-hand portion with its internal mechanism being removed to shew the rollers whereby the swash-plate is actuated. Figure 3 is an internal face view of the plate which carries the inlet and delivery valves and serves to close the forward ends of all the pump cylinders. Figure 4 is a partial view, corresponding to the lower right-hand portion. of Figure 1 and shewing means for temporarily preventing the ejection of a piston from its cylinder by the action of its spring.

The driving shaft 11 is journalled in a bearing 12 at the end of the casing 13, and has fast upon it a disc 14 serving as a flywheel, this disc being provided with a circumferential series of four angularly equidistant pillars 15, 16 17, 18 whlch carry,

on radially disposed axle'pins 19, as many freely rotatable rollers 15, 16, 17, 18. These rollers for a purpose hereinafter explained, are made of equal effective diameters, but their axes 19, are set at such varying distances from a plane of revolution of the flywheel 14 as to permit of all the rollers maintaining contact with an annular track 20 on the rear face of a swash-plate 21 mounted to wobble upon a ball 22 seated in a depression on the rear end of a screw 23 which extends, coaxially with the shaft 11, through the cylinder block 24 wherein it is adjustably locked by a nut 25. Theaxial thrust exerted through the swash-plate 21, the rollers, and the flywheel 14, against the shaft 11' is borne by a ball thrust bearing 26 in contact with which a circular track 27 at the rear of the flywheel is fitted'to rotate.

The cylinder block 24, to the rear face of which the casing 13 is attached, is formed with a circular series of four equidistant cylindrical bores 28, in each of which a piston 29 is fitted to reciprocate; each piston tending constantly to move rearwards under the action of a spring 30 coiled about a conical rearward extension 31 of the piston and confined in compression between the rear face of the cylinder block 24 and a washer 32 held against the rear extremity of the piston extension 31 by means of a set screw 33 which is locked in position by 'a nut 34 countersunk in the forward face of the piston 29. The head 35 of each set screw 33 is domed to contact with the forward face of the swash-plate 21.

The periphery of each of the rollers 15, 16, 17, 18 is formed as the frustum of a sphere, the radius of the sphere being the same for all the rollers, and the annular track 20 on the rear face of the swash-plate 21 has a concave cross-section curved to the same radius; the arrangement being such that, during working, line-contact is maintained between the track 20 and each roller in all positions of the flywheel 14 and swash-plate 21 relatively to one another. For this purpose, the one pair of oppositely-placed rollers 16, 18, whereof the axle-pins 19 are set at equal distances from a plane of revolution of the flywheel 14, are formed each as a central or symmetrical frustum of the sphere and are also mounted at equal radial distances from the axis of the shaft 11, so as to be adapted to run constantly in contact with the middle portion of the width of the track 20; whereas the other pair of oppositely-placed rollers 15, 17, whereof the axlepins 19 are set at respectively a lesser and a greater distance from said plane of revolution, are formed each as a non-central or non-symmetrical frustum of the sphere, and

are also mounted at respectively a lesser and a greater radial distance from the axis of the shaft 11, so as to be adapted to run constantly in contact with the inner and the outer portions respectively of the width of the track 20.

In the outer side of the wall of each cylinder-bore 28 is formed a threaded hole 36 closed by an adjustable screw 37 which is normally retracted outwards as in Figure 1; the hole 36 being so placed lengthwise of the stroke of the piston 29 that, when the pistonis forced forward a ainst its spring 30 (as at the lower side of Figure 1 the screw 37 can be caused to project as in Figure 4) into the interior of the cy inder so as to be encountered, on the release of the spring, by the shoulder presented at the junction of the conical portion 31 with the cylindrical portion of the piston. By this means, during the assembling of the parts, each piston can be prevented from being ejected rearwards by its spring, after the piston, with its rings, has once been inserted in its cylinder and the spring mounted in operative position; and similarly but conversely, during demounting, all the pistons can be locked against ejection, 'prior to the cylinder block 24 with the several pistons and springs being detached from the casing 13.

The cylinder block 24 may be formed externally with fins 38 to promote cooling by radiation. 39 (Figure 2) indicates the position of a breathing aperture provided in the casing 13, the aperture being preferably furnished with a screen of wire gauze.

The front ends of all the cylinders 29 are closed by a single plate 40 fixed to the cylinder block 24 and carrying the inlet and delivery valves appertaining to each cylinder, the plate 40 being hollow and its interior being divided by an annular partition 41 into a central inlet chamber 42 surrounded by an annular delivery chamber 43. The inlet chamber 42 is in free communication with the external atmosphere by way of a central opening 44 furnished with a screen 45 of wire gauze, whilst the delivery chamber 43 communicates by a pipe 46 with the point of delivery. Opposite to each cylinder 28 there are arranged, in the inner wall 40 of the hollow plate 40, an inwardly-opening, normally spring-closed, inlet valve 47 of the usual mushroom type, controlling an opening which leads from the cylinder to the interior of theinlet chamber 42; and also an outwardly-opening, normally spring-closed, outlet valve 48 controlling an opening which leads from the cylinder to the interior of the delivery chamber 43.

It will be observed that the improved construction enables the overall length of the pump to be reduced, and that it facilitates considerably the assemblage of the parts,

eaaaae and their demounting for the purpose of repair should necessity arise. Moreover it is possible to put, and to retain, one or more cylinders out oi action if it be found desirable so to do.

I claim 1. In a multiple-cylinder pump, the combination of a plurality of reciprocating pistons, asWash-plate, springs for moving said pistons outward to maintain operative engagement with said swash-plate, and a rotatable driving member carrying a plurality of rollers for operating said swash-plate, said rollers being of the same diameter and formed with spherical Working faces adapted to cooperate With a correspondingly curved annular groove on said swash-plate.

2. The pump as claimed in claim 1, Wherein the respective rollers are mounted on said rotatable member at difierent distances from the axis of rotation thereof, and at difierent distances from a plane at right angles to said axis of rotation.

REGINALD DONOVAN BOYCE. 

